We visited the HoF in Cooperstown today, this was our third visit and it never ceases to amaze. The Nats display though is sorely lacking, most of the stuff is pretty old - Alfonso Soriano's jersey, Zimm's cap from the opening game at Nats park, and a few other older items. The newest item is the first ball Strasburg threw in his debut. They also had Willingham's bat from his 2 GS game a few years back. Of course there's plenty of Senators/Expos stuff, as well as Livo's world series jersey with the fish.
As I posted on the Harper compendium thread, many of the memorabilia shops in Cooperstown had Harper stuff in the window displays. Signed Harper baseballs were going for $150-200. I saw a Ryan Zimmerman rookie card for $5.00. One shop had a 3-for-$15 bin of signed cards. I saw Maxwell, Mock, Flores, Bergman, and Bally in there along with a few others I can't recall. One shop had a framed commemorative plaque from Strasburg's debut, including dirt from the field and pictures with a brass plaque for $95.
If you haven't been there, it's worth the trip.